Many prosthetic mechanical heart valves have previously been used as surgically implantable replacements for malfunctioning endogenous anatomical heart valves.
One particular type of prosthetic mechanical heart valve is known as a "bileaflet" mechanical valve. Bileaflet type mechanical valves typically comprise a pair of flat occluder leaflets pivotally mounted within a ring-like annular valve body. The annular valve body is sutured into the heart (typically at the mitral or aortic position), as a replacement for a surgically removed endogenous valve. The occluder leaflets are pivotally mounted within the annular valve body such that the leaflets will move back and forth, in response to hemodynamic forces of the blood, between an "open" position whereby blood is permitted to flow through the annular valve body in a first direction, and a "closed" position whereby blood is prevented from backflowing in a second direction opposite said first direction.
In any prosthetic mechanical valve of the bileaflet type, it is desirable that the components of the valve be designed, configured and constructed so as to minimize or prevent stagnation or lodging of blood within the valve, as such stagnation or lodging of blood may give rise to thrombus formation and resultant thromboembolic complications. In bileaflet-type mechanical valves, one specific region where blood has been known to lodge or stagnate in crevices or notches formed as part of the hinge or pivot mechanism whereby the occluder leaflets are pivotally mounted within the annular valve body. In efforts to minimize such lodging or stagnation of blood, some of the bileaflet mechanical valves of the prior art have incorporated pivot/hinge mechanisms which are purportedly designed to perform a self-clearing or self-wiping function to dislodge blood which may tend to stagnate or lodge within the pivot/hinge mechanism of the valve.
Additionally, it is desirable that bileaflet mechanical prosthetic valves be designed so that the leaflets will open and close softly, without slamming or unnecessary surface-to-surface contact of a type likely to cause hemolysis (i.e., the breaking or rupture of blood cells).
Furthermore, it is desirable that heart valves of the bileaflet type be configured and constructed to withstand long term usage and wear, without fatigue, breakage or fracture of the valve components.
Examples of prosthetic mechanical heart valves of the prior art include those described in the following U.S. Pat. Nos.: 4,178,639 (Bokros), 4,272,854 (Bokros), 4,276,658 (Hanson, et al.), 4,328,592 (Klawitter), 4,363,142 (Meyer), 4,373,216 (Klawitter), 4,443,894 (Klawitter), 4,451,937 (Klawitter), 4,605,408 (Carpentier), 4,446,577 (Meyer, et al.), 4,676,789 (Sorensen, et al.), 4,692,165 (Bokros), 4,822,353 (Bokros), 4,863,458 (Bokros), 4,863,459 (Olin), 4,872,875 (Hwang), 4,888,010 (Bokros), 4,892,540 (Vallana), 4,923,465 (Knoch, et al.), 4,935,030 (Alonso), 4,995,881 (Knoch, et al.), 5,002,567 (Bona, et al.), 5,061,278 (Bicer), 5,078,738 (Couetil), 5,108,425 (Hwang), 5,116,366 (Hwang), 5,116,367 (Hwang, et al.), 5,123,920 (Bokros), 5,137,532 (Bokros, et al), 5,147,390 (Campbell), 5,152,785 (Bokros, et al.), 5,171,263 (Boyer, et al.), 5,178,632 (Hanson), 5,192,309 (Stupka, et al.), 5,192,313 (Budd, et al.), 5,197,980 (Gorshkov, et al.), as well as the following foreign patents and foreign patent publications: EP238181A, WO 86/05383, WO 91/11973, 0091746, 0465383A1, 0541215A1, WO 92/21305, 0023797, GB2055,452A, 0050439, GB2018396A, 0515324A1, WO92/02197, 0327790, EP289494, EP133608A, WO93/01767, EP89104A, EP256047A, EP436420A, EP 403649A, WO90/04367, EP176237A, and WO91/05524.
Although the prior art has included numerous surgically implantable bileaflet mechanical heart valves, there remains a need in the art for the development of new or improved bileaflet mechanical valves capable of long term, cardiac functioning with minimal likelihood of thromboembolic complications or other untoward side effects.